The present invention is related to an improved ratchet structure of a screwdriver, and more particularly to a ratchet structure in which the middle sections of the left and right dogs of the ratchet mechanism are respectively supported by projecting sections of a seat body. By means of turning the cap member, the swinging positions of the left and right dogs can be switched so as to more truly and conveniently operate the ratchet mechanism.
FIGS. 6 to 8 show a conventional ratchet screwdriver. The handle 8 is formed with a cavity 81 through which a stem 82 is fitted. A section of the stem 82 in the cavity 81 is a toothed section 821. The handle 8 is further formed with two pairs of radially opposite chambers 83 communicating with the cavity 81. A leaf spring 84 and a dog 85 are disposed in each chamber 83. The leaf spring 84 pushes the dog 85 to engage with the toothed section 821 of the stem 82. The center of inner face of the upper cap 86 is formed with a circular projecting block 87. The projecting block 87 has two radially oppositely extending projecting sections 871. When turning the upper cap 86, the two projecting sections 871 respectively push away the opposite dogs 85 to change the rotational direction of the stem 82 driven by the handle 8. In addition, the inner side of the upper cap 86 is formed with a projecting locating block 88. The handle 8 is formed with three locating sections 89 corresponding to the locating block 88. The locating sections 89 are respectively formed in three positions where different dogs 85 are respectively pushed away by the projecting sections 871 of the projecting block 87 and where no dogs 85 are pushed away by the projecting sections 871. Accordingly, the locating block 88 can locate the upper cap 86 in any of the three positions.
According to the above structure, the two projecting sections 871 of the circular projecting block 87 extend radially opposite to each other. The edges of the projecting sections 871 are formed with two guide faces 872 adjacent to the projecting block 87. A stop face 873 is formed between each two guide faces 872. The four chambers 83 also radially extend as the projecting sections 871. Therefore, the guide faces 872 are nearly parallel to the lateral sides of the dogs 85 disposed in the chambers 83. As a result, it is laborious to turn the upper cap 86 and make the guide faces 872 of the projecting sections 871 push away the dogs 85. Furthermore, under limitation of the dimension of the cavity 81, the size of the projecting sections 871 cannot be freely enlarged. Accordingly, when turning the upper cap 86 to make the stop faces 873 of the projecting sections 871 respectively push away the dogs 85, the dogs 85 are retracted into the chambers just in flush with the outer circumference of the cavity 81 as shown in FIG. 8. The toothed section 821 of the stem 82 can just pass over the dogs 85. However, after a period of use, the stop faces 873 will be inevitably worn and depressed, so that the stop faces 873 will be unable to fully push the dogs 85 away from the cavity 81. As a result, the toothed section 821 of the stem 82 will collide the dogs 85 and the ratchet mechanism can be hardly truly operated.
It is therefore a primary object of the present invention to provide improved ratchet structure of a screwdriver in which the middle sections of the left and right dogs of the ratchet mechanism are respectively supported by the projecting sections of the seat body. In addition, the left and right dogs are respectively pushed by two springs to engage with the toothed section of the stem. When turning the cap member, the projecting block in the cap member can easily push and deflect the left dog or right dog and truly disengage the left dog or right dog from the toothed section of the stem. Accordingly, the ratchet screwdriver can be more conveniently and truly operated.
It is a further object of the present invention to provide the above ratchet structure in which the steel ball disposed in the receptacle and the two ball bodies disposed in the left and right through holes together support the inner circumference of the cap member so as to reduce the frictional resistance against the cap member when turned. Therefore, the cap member can be more smoothly turned.
The present invention can be best understood through the following description and accompanying drawings wherein: